Note to Editors: The complete hurricane forecast report, related research, detailed descriptions of forecast factors, charts and previous forecasts will be available on the Web at http://www.colostate.edu or http://hurricane.atmos.colostate.edu no later than 8 a.m. MST.
El Nino conditions that led to a quiet hurricane season in 2006 are likely to dissipate by next summer, leading to above-average hurricane activity for 2007, according to the early season forecast issued today by Colorado State University’s forecasting team.
The United States faces another active Atlantic basin hurricane season in 2007, but with likely fewer landfalling intense hurricanes than in 2005 – the costliest, most destructive hurricane season ever, said Philip Klotzbach, William Gray and the Colorado State University forecast team, who issued their 24th forecast today.
The team’s first extended-range forecast for the 2007 hurricane season anticipates 14 named storms forming in the Atlantic basin between June 1 and Nov. 30. Seven of the 14 storms are predicted to become hurricanes, and of those seven, three are expected to develop into intense or major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.
No hurricanes hit the U.S. coastline in 2006 – only the 11th time that has occurred since 1945.
In contrast, the 2005 season witnessed 27 named storms, 15 hurricanes and seven intense hurricanes. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
"The 2007 Atlantic hurricane season is expected to be more active than the average 1950-2000 season," Klotzbach said. "However, this is an early prediction. One of the important questions for the upcoming season is whether El Nino conditions will continue through 2007."
Late-developing El Nino conditions contributed to a calmer 2006 hurricane season. But Klotzbach notes that seven of eight seasons following El Nino conditions in an active Atlantic multi-decadal period were active Atlantic hurricane seasons.
The entire report is available on the Web at http://hurricane.atmos.colostate.edu.
"Despite a fairly inactive 2006 hurricane season, we believe that the Atlantic basin is in an active hurricane cycle," Gray said. "This active cycle is expected to continue for another decade or two at which time we should enter a quieter Atlantic major hurricane period like we experienced during the quarter-century periods of 1970-1994 and 1901-1925."
The CSU hurricane forecast team also predicts a 64 percent chance that at least one major hurricane will make landfall on the U.S. coastline in 2007. The long-term average probability is 52 percent.
For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 40 percent (the long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle west to Brownsville, the probability is 40 percent (the long-term average is 30 percent).
Florida and the Gulf Coast were ravaged by four landfalling hurricanes in 2004 and 2005. Hurricanes Charley, Frances, Ivan and Jeanne caused devastating damage in 2004, followed by Dennis, Katrina, Rita and Wilma in 2005.
Gray has said that it would be statistically unlikely that two years in the near-future hurricane seasons would have the number of U.S. landfalling major hurricanes seen in 2004 and 2005.
Along with today’s report, the team has updated the Landfall Probability Web site that provides probabilities of tropical storm-force, hurricane-force and intense hurricane-force winds making landfall at specific locations along the U.S. East and Gulf Coasts within a variety of time periods. U.S. landfall probabilities are available for 11 regions, 55 sub-regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine.
The Web site, available to the public at http://www.e-transit.org/hurricane, is the first publicly accessible Internet tool that adjusts landfall probabilities for regions, sub-regions and counties based on the current climate and its projected effects on the upcoming hurricane season. Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts.
The hurricane team’s forecasts are based on the premise that global oceanic and atmospheric conditions – such as El Nino, sea surface temperatures and sea level pressure – that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.
For 2007, Gray and the hurricane forecast team expect continued warm tropical and north Atlantic sea-surface temperatures, prevalent in most years since 1995, as well as neutral or weak La Nia conditions – a recipe for greatly enhanced Atlantic basin hurricane activity. These factors are similar to conditions that occurred during the 1952, 1958, 1966 and 2003 seasons. The average of these four seasons had well above-average activity.
"Recent or projected Atlantic hurricane activity is likely not linked to human-induced global warming," Gray said.
"Despite the global warming of the sea surface that has taken place over the last three decades, the global numbers of hurricanes and their intensity has not shown increases in recent years except for the Atlantic," Gray said.
The team will issue seasonal updates of its 2007 Atlantic basin hurricane activity forecast on April 3, May 31, Aug. 3, Sept. 4 and Oct. 2. The August, September and October forecasts will include separate forecasts for each of those months.